Bench-scale study of separation of hydrogen from gasification gases using a palladium-based membrane reactor

Abstract

The aim of this work was to study separation of hydrogen from the main components of syngas, i.e. synthesis gas from gasification of e.g. coal, biomass or wastes. Experiments were performed in a bench-scale facility designed to treat up to 2m3h−1 (STP) at 873K, and 1.2MPa. A Pd-based membrane (O.D.=0.0254m; L=0.15m) from CRI Catalyst Co., US was used.Firstly the membrane was tested in pure hydrogen experiments. Permeation was determined as a function of pressure and temperature. An increase of pressure resulted in an increase of permeation. An increase of temperature also enhanced permeation.The presence of nitrogen or carbon dioxide resulted in a decrease of hydrogen permeation. Carbon dioxide inhibited hydrogen permeation to a slightly higher extent than nitrogen, and in addition the reverse water–gas-shift WGS reaction was found to be taking place. Steam also led to a decrease of hydrogen permeation. The effect of carbon monoxide was also analysed. At 723K, it did not modify hydrogen permeation, regardless carbon monoxide content in the feed gas. A strong inhibition was noticed, however, on decreasing operating temperature. Production of a pure hydrogen permeate stream was achievable even when a mixture similar in composition to a synthetic unconverted shift gas was fed to the reactor. However, hydrogen recovery was smaller.